Art of cracking hydrocarbons



Nov. 1%, 19371 E. c. HERTHEL 2,099,426

ART OF CRAGKIKG HYDROCARBONS Filed April 23,' .1932

INVENTOR Faye/7e C flew 1% e/ I ATTORNEYS Patented Nov. 16, 1937 i UNITED STATES 2,099,426 r ART 'OFCRACKING HYDROCARBONS Eugene HertheLl hssmoor, 111,, assignorto, Sin

clair Refining Company, New York, N. Y., a.

corporation of Maine Application April 23, 1932,- Serial Nit-07,091

duction of such gases constitutes a loss in that it is "the production of a product less valuable than gasoline and also imposes a burden on subsequent operations for direct fractionation of the liquid products. Severe cracking, however, is an advantageous means of producing motor'fuel gasoline o'f'high anti-knock value. The increased production of incondensible gases incident to such severe cracking is offset input by the improved value" of. the gasoline'produced and can be'further' ofiset'by recracking of the incondensible gases under conditions appropriate'to produce additional gasoline.

According to the pres'ent'nvention a gas mixture isseparated from the products of the primary cracking under a maintained superatmosphericpressure upwards of about 600 pounds per square-inch and the separated "gas'm'ixture is supplied to "the secondary cracking under the pressure of separation and without compression,

and the liquid product of the primary cracking is fractionated after the gas mixture has been separated. *Twoimportant advantages are thus secured. The necessity for compressingor recompressingthe gas mixture supplied to the secondary cracking is eliminated. The subsequent fractionation of the separated liquid products is improved by elimination of the separated gas mixture. The primary cracking may be any conventional cracking operation in which'the 'crackedproducts are dis'cha rged' under a superatmospheric pressure upwards of about 600 pounds per square'inch. The'secon'd'ary cracking may be any conventional operation for recracking such gas mixtures. r

*The invention will be further described in connection with the accompanying drawing which,

illustrates, diagrammatically and conventionally, one form of apparatus embodying and adapted for carrying out the process of the invention. Referring to the drawing, the apparatus illustrated comprises a primary cracking heater I, a secondary cracking heater 2, a reheater 3, a separator l, an evaporator 5, a battery of digesting drums 6, fractionating towers l and 8, condensers Qjand Ill, receivers ll and-l2, and pump l3.

Oil to be cracked is supplied to the cracking heater I through connection I4 by means of pump-l3; This-oil mayconsist, for example, ex clusively of raw stock to be cracked supplied through connection H3, or exclusively of condensate separated in the fractionating tower I supplied through connection 16, or of a mixture of such raw stock and condensate. This oil is forced as a stream through the cracking heater I, and by means of connection ll, into the separator 4'against a superatmospheric pressure upwards of 600 pounds 'per'square inch, 650-700 pounds per squareinch for example, maintained in the separator 4.; The oil may be heated, for example, to a cracking temperature of 910-985 F; in thecracking heater l.- The temperature in the separator 4-is with advantage maintained low enough, 650-750 F. for example, to maintain liquid under the prevailing pressure a substantial part of the gasoline constituents formed in the cracking heater I. The bulk of the gasoline'constituents formed in the cracking heater I may, by appropriate temperature control, be maintained liquid under the prevailing pressure in the separator 4, or a part ofthese gasoline constituents maybe separated'with the gas mixture separated in the separator 4. The maintenance of this temperature is with advantage effected bytheregulated introduction, into the separator, of relatively cooler petroleum oil. Such relative- 1y cooler oil'may, for example, be introduced into the separator-4 through any one or more of the connections I8, I9, '20 and 2|. Part of the oil to be cracked may be by-passed through connection [8 directly into the separator 4 without passing through the cracking heater I. Condensate separated in the fractionating tower I, supplied through connections l6 and 22, may be introduced into the separator 4 through connection l9, connection 20 or connection 2! or any two or three of these connections, by means of pump 23.- A separate stock, raw stock to be cracked for example, supplied through connection 24, may be introduced into the separator 4 through anyone or' more ,of the connections [9, Ill-and 2| by means of pump 23, either alone or in admixture with condensate supplied through connection 22. A particularly advan tageous control of the separation of the gas mix: ture is thus provided. The gas mixture separated in the separator 4 is supplied to the cracking heaterF-Z, through connection 25, and forced through the cracking heater 2 and the connected battery of digesting drums 6 into the fractionating tower 8 by means of the pressure maintained in the separator 4. Compression or recompression of the gas mixture supplied to the cracking heater 2, to maintain the appropriate superatmospheric pressure in the cracking heater 2 and in the connected battery of digesting drums 6 is thus avoided. The liquid material separated in the separator 4 is discharged through connections 26 and 21, the latter ineluding a pressure controlling and reducing valve 28, into the evaporator 5. This liquid material may be discharged directly into the evaporator from the separator 4 or, if additional heat is necessary to effect the desired vaporization in the evaporator 5, it may be passed through the reheater 3 on its way from the separator 4 to the evaporator 5. Lower boiling constituents of the liquid material discharged into the evaporator 5 through connection 21 are vaporized therein and discharged, as a vapor mixture, into the fractionating tower 1 through connection 29, the vaporization in the evaporator 5 being effected entirely or in part by means of the self-contained heat of the oil discharged from the separator 4, a substantially lower pressure being maintained in the evaporator 5 than in the separator 4. If the separator 4 is maintained under a pressure of 650-700 pounds per square inch for example, the evaporator 5 may be maintained under a pressure of 5-60 pounds per square inch for example. Steam may be supplied through connection 30 to assist or to control vaporization in the evaporator 5. The residual liquid material separated in the evaporator 5 is discharged through connection 31.

In the cracking heater 2, the gas mixture discharged from the separator 4 is heated to a cracking temperature, 930-1120 F. for example, under a superatmospheric pressure approximating 400-600 pounds per square inch, for example,

' or under a somewhat higher superatmospheric pressure. The cracking heater 2 and the battery of digesting drums 6 may be arranged in a combined furnace setting, as in the apparatus illustrated and described in Pelzer Patent No. 1,949,655, or the battery of digesting drums may be arranged in a separate furnace setting or in a thermally insulated chamber as in the apparatus illustrated in the drawing, or the digesting drums may be dispensed with if a suflicient period of reaction is provided in the cracking heater proper. The products of the secondary cracking are discharged from the battery of digesting drums 5, or from the cracking heater 2 if the battery of digesting drums 6 be dispensed with, through connection 32 into the fractionating tower 8. This material may include some tar constituents as well as some constituents higher boiling than suitable as components of gasoline. Such higher boiling constituents, including any tar constituents, are separated in the fractionating tower 8 from which they are discharged through connection 33. This material, condensate or tar mixture, may be introduced, in whole or in part, into the separator 4 through one or more of the connections 2|, 20 and 19 by means of pump 34 or it may be discharged, in whole or in part, through connection 35. Tar constituents so introduced into the separator 4 are ultimately discharged from evaporator 5 through connection 31. The operation of the fractionating tower 8 may be controlled by the refluxcondenser 36 or by the introduction of a direct refluxing agent through connection 31 or by both of these means conjointly. If a direct refluxing agent is used, the use of an extraneous refluxing agent, as described in Letters Patent Number 1,711,351, granted to Sinclair Refining Company, April 30, 1929, on an application of Edward W. Isom, is advantageous. The gasoline vapor mixture produced in the secondary cracking passes from the fractionating tower 8 to the condenser 19 through connection 38. The condenser I9 discharges into the receiver 12 in which the gasoline condensate is separated from uncondensed vapors and gases. The gasoline condensate is discharged through connection 39 and the uncondensed vapors and gases through connection 40.

The vapor mixture separated in the evaporator 5 is fractionated in the fractionating tower 1 to produce an overhead gasoline vapor mixture and one or more higher boiling condensate fractions. The gasoline vapor mixture separated in the fractionating tower 1 passes to the condenser 9 through connection 4|. The condenser 9 discharges into the receiver H in which the gasoline condensate is separated from the uncondensed vapors and gases. The gasoline condensate is discharged through connection 42 and uncondensed vapors and gases through connection 43. The operation of the fractionating tower 1 is controlled either by the reflux condenser 44 or by the direct introduction of a refluxing agent through connection 45 or by both of these means conjointly. A part of the gasoline condensate separated in the receiver H may be supplied, through connections 45 and 45 by means of pump 41, as a refluxing agent or an extraneous refluxing agent may be supplied through connections 48 and 45 by means of pump 41.

The uncondensed vapors and gases separated in either or both of the receivers H and I2 may be subjected to suitable operations for the recovery of their content of very low boiling gasoline constituents. Any conventional recovery operation may be employed for this purpose. The recovery operation described in Letters Patent Number 1,705,077, granted to Sinclair Refining Company, March 12, 1929, on an applicationv of George H. Taber, Jr., may with advantage be employed in conjunction with the fractionating operation carried out in the fractionating tower 1.

In one aspect this invention provides an improvement independent of the secondary cracking. The separation of the gas mixture produced by the primary cracking under a maintained pressure upwards of about 600 pounds per square inch, for example, and at a temperature low enough to maintain liquid under the prevailing pressure the bulk of the gasoline constituents formed in the primary cracking, the temperature being controlled by the introduction, into the separator, of relatively cooler petroleum oil, makes possible improved subsequent fractionation of the separated liquid products by elimination of the separated gas mixture. The separated gas mixture, may in this aspect of the operation, be subjected to'suitable' operations for the recovery of its content of very low boiling gasoline constituents.

I claim: 7

1. In the manufacture of gasoline, the improvement which comprises forcing a stream of higher boiling petroleum oil through a heating Zone into a separator maintained under a superpounds per square inch and heating the oil to atmospheric pressure upwards of about 600 ture-t'nrough a separate heating zone by means a of the pressure, maintained in the separator and heating the gas mixture to a cracking tempera-" ture under a substantial superatmospheric pressure in the separate heating zone, discharging the liquid material separated in the separator into an evaporator maintained under a pressure substantially lower than thatunder which the separator is maintained and thereby vaporizing lower boiling constituents, separately taking ofi vapors from said evaporator and introducing them directly to a refluxing zone;'condensing in said refluxing zone higher boiling constituents of the vaporized constituents and supplying the condensate to the first mentioned heating zone, and condensing and collecting the gasoline constituents vaporized from the separated liquid material in said evaporator which remains uncondensed in said refluxing zone and those gasoline con- 'stituents formed from the separated gas mixture.

2. In the manufacture of gasoline, the improvement which comprises forcing a stream of higher boiling petroleum oil through a heating zone into a separator maintained under a superatmospheric pressure upwards of about 600 pounds per square inch and heating the oil to a severe cracking temperature in the heating zone, maintaining the separator at a temperature low enough to maintain liquid under the prevailing pressure a substantial part of the gasoline constituents formed in the heating zone and separating a gas mixture from liquid material in the separator, forcing this separated gas mixture through a separate heating zone by means of the pressure maintained in the separator and heating the gas mixture to a cracking temperature under a substantial superatmospheric pressure in the separate heating zone, discharging the liquid material separated in the separator into an evaporator maintained under a pressure substantially constituents, separately taking ofi from said evaporator the lower boiling constituents vaporized therein, and condensing and collecting the gasoline constituents so vaporized from'the separated liquid material and those formed from the separated gas mixture.

3. In the manufacture of gasoline, the improvement which comprises forcing a stream of higher boiling petroleum oil through a heating zone into a separator maintained under a superatrnospheric pressure upwards of about 600 pounds per square inch and heating the oil to a severe cracking temperature in the heating zone, maintaining the separator at a temperature low enough to maintain liquid under the prevailing pressure a substantial part of the gasoline constituents formed in the heating zone by the introduction into the separator of relatively cooler petroleum oil and separating a gas mixture from liquid material in the separator, forcing this separated gas mixture through a separate heating zone by means of the pressure maintained in the separator and heating the gas mixture to a cracking temperature under a substantial superatmospheric pressure in the separate heating zone, discharging the liquid material separated m the 'separator' -into an evaporator maintained under a pressure substantially lower than that under which the separator is maintained and thereby, vaporizing-- lower boiling constituents, separately 'taking off from'said'evaporator the lower boiling constituents vaporized therein, and condensing and-collecting the gasolineconstituentsso vaporized from the separated'liquid material and'thoseiormedfromthe separated gas mixture. j V I I 7 4. In the manufacture of gasoline, the improvement which comprises' forcing a stream of higher boiling petroleum oil through a heating zone into a separator maintained under a superatmospheric pressure upwards of about 600 pounds per square inch and heating the oil to a severe cracking temperature in the heating zone, separating a gas mixture from liquid material in the separator and controlling the separation by the introduction into the separator of relatively cooler petroleum oil, forcing this separated gas mixture through a separate heating zone by means of the pressure maintained in the separator and heating the gas mixture to a cracking temperature under a substantial superatmospheric pressure in the separate heating zone, discharging the liquid material separated in the separator into an evaporator maintained under a pressure substantially lower than that under which the separator is maintained and thereby vaporizing lower boiling constituents, separately taking oif from the evaporator the vapors separating therein and condensing and collecting without further cracking treatment thereof the gasoline constituents in said vapors, and condensing and collecting gasoline constituents -formed from the separated gas mixture.

5. In the manufacture of gasoline, the improvement which comprises forcing a stream of higher boiling petroleum oil through a heating zone into a separator maintained under a superatmospheric pressure upwards of about 600 pounds per square inch and heating the oil to a severe cracking temperature in the heating zone, separating a gas mixture from liquid material in the separator and controlling the separation by the introduction into the separator of relatively cooler petroleum oil, forcing this separated gas mixture through a separate heating zone by means of the pressure maintained in the separator and heating the gas mixture to a cracking temperature under a substantial superatmospheric pressure in the separate heating zone, discharging the liquid material separated in the separator into an evaporator maintained under a pressure substantially lower than that under which the separator is maintained and thereby vaporizing lower boiling constituents, separately taking off from said evaporator the lower boiling constituents vaporized therein, condensing higher boiling components of the material'vaporized in said evaporator including constituents vaporized in the evaporator from the oil introduced directly into the separator and supplying the condensate to the first mentioned heating zone, and condensing and collecting without further cracking the gasoline constituents taken off as vapors from said evaporator and condensing and collecting the gasoline constituents formed from the separated gas mixture.

6. In the manufacture of gasoline, the improvement which comprises forcing a stream of higher boiling petroleum oil through a heating zone into a separator maintained under a superatmospheric pressure upwards of about 600 the separate heating zone, separating tar formed in the separate heating zone and introducing such tar directly into the separator, discharging the liquid material separated in the separator into an evaporator maintained under a pressure substantially lower than that under which the separator is maintained and thereby vaporizing lower boiling constituents, and condensing and collecting the gasoline constituents so vaporized from the separated liquid material and those formed 10 from the separated gas mixture.

EUGENE C. HERTHEL. 

